The annual sing-along started earlier than usual this year, in late July rather than early August.

"Everything's earlier this year," Henry said. "Spring came early. And we avoided catastrophic weather in summer. The dry spell we had went away."

What we're hearing at night -- mostly -- are two insect cousins: crickets and katydids. Both are in the family called long-horned grasshoppers.

Henry said both species rub their wings together to make the sounds we hear. Katydids make the raspy creaking calls that fill the night.

"Crickets make a more musical song," Henry said.

During the day, short-horned grasshoppers start singing. They rub the edge of their leg against their wing to make a sound.

"It's like a file and scraper," Henry said. "The file is on the leg. The scraper is on the wing."

In late August, he said, we hear tree crickets. They chew holes in leaves, stick their heads in the hole, then vibrate their wings. The sound bounces off the leaves and gets louder.

"It's like a baffle in an amplifier that lets you hear the bass sounds," Henry said. "Tree crickets use leaves as their baffle."

And finally, in August, there's the high steady trill of the annual cicadas -- also known as "dog-day cicadas," for the dog days of August.

Henry said some areas of the United States have periodic, massive infestations of cicadas. They mature underground then suddenly emerge in huge, riotous, messy swarms.

In Connecticut, he said, entomologists don't know how long cicadas spend growing up underground -- it might be five years, it might be seven or more.

But every year some emerge. Rather than rubbing their wings or legs, they come equipped with their own noisemakers -- called tymbals -- on the sides of their body. When cicadas breathe, the tymbals contract and expand, making a clicking noise that creates the long single-note cicada song. Their bodies act as amplifiers.

All of this singing and chirping and buzzing comes from the males. Like operatic tenors, like sad-eyed singer-songwriters, like rock balladeers or blues shouters, they sing to attract females for mating.

Henry said researchers don't know if it is simply the loudest of the bunch that the females head toward, or whether they are swayed by a particular tonal quality. But they do find a singer they like -- or several. They can lay several egg masses a season.

The night chorus lasts into September or early October.

"They live and sing and mate," Henry said. "Then we get a frost, and it's all over for the year."